Puffins being wiped out as shrub chokes nesting sites

One of Britain's best-known seabirds, the puffin, is being wiped out by invading fast-growing alien plant species because of global warming.

Scientists have discovered the tree mallow is choking puffin breeding sites on Scottish islands and have warned that the plant could soon start killing off other seabirds, such as herring gulls and cormorants.

Tree mallow, Lavatera arborea, which grows mainly in Mediterranean countries, was once confined to only a few UK outcrops.

But now the plant has begun to spread as a result of global warming. This year was the northern hemisphere's hottest on record. Polar bears and Arctic seals are suffering. In southern England, frogs have started to spawn and autumn leaves have failed to fall.

'The plant has already covered a couple of islands so thickly that puffins cannot make their nests on the ground,' said Dr René van der Wal, of the Centre for Ecology and Hydrology, in Banchory.

'They cannot burrow in the soil and make nests. The result has been a catastrophic decline in puffin breeding.'

On Craigleith, near North Berwick, the numbers of burrows in which puffins breed plunged from 28,000 in 1999 to 14,000 in 2004 and the drop has continued this year, added van der Wal.

'This is now the most dramatic example of an alien plant invader affecting wildlife in Britain,' he told The Observer.

It is estimated that there are several hundred thousand puffins in the UK. However, half that population is restricted to only a handful of sites, making it vulnerable to environmental threats. As a result, the puffin is on the Royal Society of the Protection of Bird's amber list of threatened species.

The Atlantic puffin, Fratercula arctica, has a black back and white underparts, a flattened, brightly-coloured bill, and red and black eye-markings with bright orange legs. It is one of the nation's most distinctive and popular birds and is often photographed with sand eels - its favourite food - hanging out its bill. The record is held by one bird which was found with 61 sand eels in its beak.

But the advance of the tree mallow has added new fears for its future. First Craigleith succumbed to the plant, now nearby Fidra - said to be the island on which Robert Louis Stevenson based Treasure Island - has begun to acquire a thick, impenetrable layer of tree mallow. Now the plant has started colonising other Scottish isles.

'The puffin only makes things worse for itself,' added van der Wal. 'It breaks up the ground, providing a perfect place for tree mallow seeds to take root. The birds provide homes for tree mallow which then prevents them breeding. Nature can be cruel.'

At present, only puffins have been affected by the tree mallow's spread. However, researchers warn other ground-nesting seabirds could soon be affected, including herring gulls, black-backed gulls and cormorants.

'There is a lot the public can do to help,' added van der Wal. 'They can send us photos of coastal areas where tree mallow is growing, for example. We need to find out how quick it is spreading.'

Getting rid of the plant may be tricky, although scientists do have a cunning plan: import neutered rabbits. 'Islands with rabbits do not have tree mallow. Rabbits rip up their shoots before they can take proper root. And rabbits and puffins get on pretty well. However, too many rabbits could cause real damage and erosion - so we would neuter them first. It's simple really.'